Two small-scale municipal wastewater treatment plants (Neghelli
and Terrarossa) discharging effluents into a lagoon of great environmental
interest and highly stressed by tourism (Orbetello, Italy) were monitored
over the year 2001. We evaluated plants’ performances developing a
general efficiency indicator of removal to select the suitable purification
technology (activated sludge, Neghelli vs. rotating biodisc reactor, Terrarossa).
Unexpected, conventional technologies (activated sludge) had best
performances (84% vs. 62%) with higher removal efficiencies for dissolved
nutrients producing, on average, better final effluents. Even if Terrarossa
showed a great improvement in summertime, during winter it seemed to be
considerably affected by sea aerosol. Before the final discharge in lagoon,
effluents were phytodepurated in a pond to reduce their nutrient load. Although
data showed that the pond had further abatement efficiency over 80%, final
outlet water represented a dangerous input for the lagoon ecosystem.
